gun.c

ZIP压缩算法源代码,可以直接加入C++Project中编译调用

                return Z_BUF_ERROR;
            }
            outcnt = 0;
        }
        do {
            outbuf[outcnt++] = match[--stack];
        } while (stack);

        /* loop for next code with final and prev as the last match, rem and
           left provide the first 0..7 bits of the next code, end is the last
           valid table entry */
    }
}

/* Decompress a gzip file from infile to outfile.  strm is assumed to have been
   successfully initialized with inflateBackInit().  The input file may consist
   of a series of gzip streams, in which case all of them will be decompressed
   to the output file.  If outfile is -1, then the gzip stream(s) integrity is
   checked and nothing is written.

   The return value is a zlib error code: Z_MEM_ERROR if out of memory,
   Z_DATA_ERROR if the header or the compressed data is invalid, or if the
   trailer CRC-32 check or length doesn't match, Z_BUF_ERROR if the input ends
   prematurely or a write error occurs, or Z_ERRNO if junk (not a another gzip
   stream) follows a valid gzip stream.
 */
local int gunpipe(z_stream *strm, int infile, int outfile)
{
    int ret, first, last;
    unsigned have, flags, len;
    unsigned char *next;
    struct ind ind, *indp;
    struct outd outd;

    /* setup input buffer */
    ind.infile = infile;
    ind.inbuf = inbuf;
    indp = &ind;

    /* decompress concatenated gzip streams */
    have = 0;                               /* no input data read in yet */
    first = 1;                              /* looking for first gzip header */
    strm->next_in = Z_NULL;                 /* so Z_BUF_ERROR means EOF */
    for (;;) {
        /* look for the two magic header bytes for a gzip stream */
        if (NEXT() == -1) {
            ret = Z_OK;
            break;                          /* empty gzip stream is ok */
        }
        if (last != 31 || (NEXT() != 139 && last != 157)) {
            strm->msg = (char *)"incorrect header check";
            ret = first ? Z_DATA_ERROR : Z_ERRNO;
            break;                          /* not a gzip or compress header */
        }
        first = 0;                          /* next non-header is junk */

        /* process a compress (LZW) file -- can't be concatenated after this */
        if (last == 157) {
            ret = lunpipe(have, next, indp, outfile, strm);
            break;
        }

        /* process remainder of gzip header */
        ret = Z_BUF_ERROR;
        if (NEXT() != 8) {                  /* only deflate method allowed */
            if (last == -1) break;
            strm->msg = (char *)"unknown compression method";
            ret = Z_DATA_ERROR;
            break;
        }
        flags = NEXT();                     /* header flags */
        NEXT();                             /* discard mod time, xflgs, os */
        NEXT();
        NEXT();
        NEXT();
        NEXT();
        NEXT();
        if (last == -1) break;
        if (flags & 0xe0) {
            strm->msg = (char *)"unknown header flags set";
            ret = Z_DATA_ERROR;
            break;
        }
        if (flags & 4) {                    /* extra field */
            len = NEXT();
            len += (unsigned)(NEXT()) << 8;
            if (last == -1) break;
            while (len > have) {
                len -= have;
                have = 0;
                if (NEXT() == -1) break;
                len--;
            }
            if (last == -1) break;
            have -= len;
            next += len;
        }
        if (flags & 8)                      /* file name */
            while (NEXT() != 0 && last != -1)
                ;
        if (flags & 16)                     /* comment */
            while (NEXT() != 0 && last != -1)
                ;
        if (flags & 2) {                    /* header crc */
            NEXT();
            NEXT();
        }
        if (last == -1) break;

        /* set up output */
        outd.outfile = outfile;
        outd.check = 1;
        outd.crc = crc32(0L, Z_NULL, 0);
        outd.total = 0;

        /* decompress data to output */
        strm->next_in = next;
        strm->avail_in = have;
        ret = inflateBack(strm, in, indp, out, &outd);
        if (ret != Z_STREAM_END) break;
        next = strm->next_in;
        have = strm->avail_in;
        strm->next_in = Z_NULL;             /* so Z_BUF_ERROR means EOF */

        /* check trailer */
        ret = Z_BUF_ERROR;
        if (NEXT() != (outd.crc & 0xff) ||
            NEXT() != ((outd.crc >> 8) & 0xff) ||
            NEXT() != ((outd.crc >> 16) & 0xff) ||
            NEXT() != ((outd.crc >> 24) & 0xff)) {
            /* crc error */
            if (last != -1) {
                strm->msg = (char *)"incorrect data check";
                ret = Z_DATA_ERROR;
            }
            break;
        }
        if (NEXT() != (outd.total & 0xff) ||
            NEXT() != ((outd.total >> 8) & 0xff) ||
            NEXT() != ((outd.total >> 16) & 0xff) ||
            NEXT() != ((outd.total >> 24) & 0xff)) {
            /* length error */
            if (last != -1) {
                strm->msg = (char *)"incorrect length check";
                ret = Z_DATA_ERROR;
            }
            break;
        }

        /* go back and look for another gzip stream */
    }

    /* clean up and return */
    return ret;
}

/* Copy file attributes, from -> to, as best we can.  This is best effort, so
   no errors are reported.  The mode bits, including suid, sgid, and the sticky
   bit are copied (if allowed), the owner's user id and group id are copied
   (again if allowed), and the access and modify times are copied. */
local void copymeta(char *from, char *to)
{
    struct stat was;
    struct utimbuf when;

    /* get all of from's Unix meta data, return if not a regular file */
    if (stat(from, &was) != 0 || (was.st_mode & S_IFMT) != S_IFREG)
        return;

    /* set to's mode bits, ignore errors */
    (void)chmod(to, was.st_mode & 07777);

    /* copy owner's user and group, ignore errors */
    (void)chown(to, was.st_uid, was.st_gid);

    /* copy access and modify times, ignore errors */
    when.actime = was.st_atime;
    when.modtime = was.st_mtime;
    (void)utime(to, &when);
}

/* Decompress the file inname to the file outnname, of if test is true, just
   decompress without writing and check the gzip trailer for integrity.  If
   inname is NULL or an empty string, read from stdin.  If outname is NULL or
   an empty string, write to stdout.  strm is a pre-initialized inflateBack
   structure.  When appropriate, copy the file attributes from inname to
   outname.

   gunzip() returns 1 if there is an out-of-memory error or an unexpected
   return code from gunpipe().  Otherwise it returns 0.
 */
local int gunzip(z_stream *strm, char *inname, char *outname, int test)
{
    int ret;
    int infile, outfile;

    /* open files */
    if (inname == NULL || *inname == 0) {
        inname = "-";
        infile = 0;     /* stdin */
    }
    else {
        infile = open(inname, O_RDONLY, 0);
        if (infile == -1) {
            fprintf(stderr, "gun cannot open %s\n", inname);
            return 0;
        }
    }
    if (test)
        outfile = -1;
    else if (outname == NULL || *outname == 0) {
        outname = "-";
        outfile = 1;    /* stdout */
    }
    else {
        outfile = open(outname, O_CREAT | O_TRUNC | O_WRONLY, 0666);
        if (outfile == -1) {
            close(infile);
            fprintf(stderr, "gun cannot create %s\n", outname);
            return 0;
        }
    }
    errno = 0;

    /* decompress */
    ret = gunpipe(strm, infile, outfile);
    if (outfile > 2) close(outfile);
    if (infile > 2) close(infile);

    /* interpret result */
    switch (ret) {
    case Z_OK:
    case Z_ERRNO:
        if (infile > 2 && outfile > 2) {
            copymeta(inname, outname);          /* copy attributes */
            unlink(inname);
        }
        if (ret == Z_ERRNO)
            fprintf(stderr, "gun warning: trailing garbage ignored in %s\n",
                    inname);
        break;
    case Z_DATA_ERROR:
        if (outfile > 2) unlink(outname);
        fprintf(stderr, "gun data error on %s: %s\n", inname, strm->msg);
        break;
    case Z_MEM_ERROR:
        if (outfile > 2) unlink(outname);
        fprintf(stderr, "gun out of memory error--aborting\n");
        return 1;
    case Z_BUF_ERROR:
        if (outfile > 2) unlink(outname);
        if (strm->next_in != Z_NULL) {
            fprintf(stderr, "gun write error on %s: %s\n",
                    outname, strerror(errno));
        }
        else if (errno) {
            fprintf(stderr, "gun read error on %s: %s\n",
                    inname, strerror(errno));
        }
        else {
            fprintf(stderr, "gun unexpected end of file on %s\n",
                    inname);
        }
        break;
    default:
        if (outfile > 2) unlink(outname);
        fprintf(stderr, "gun internal error--aborting\n");
        return 1;
    }
    return 0;
}

/* Process the gun command line arguments.  See the command syntax near the
   beginning of this source file. */
int main(int argc, char **argv)
{
    int ret, len, test;
    char *outname;
    unsigned char *window;
    z_stream strm;

    /* initialize inflateBack state for repeated use */
    window = match;                         /* reuse LZW match buffer */
    strm.zalloc = Z_NULL;
    strm.zfree = Z_NULL;
    strm.opaque = Z_NULL;
    ret = inflateBackInit(&strm, 15, window);
    if (ret != Z_OK) {
        fprintf(stderr, "gun out of memory error--aborting\n");
        return 1;
    }

    /* decompress each file to the same name with the suffix removed */
    argc--;
    argv++;
    test = 0;
    if (argc && strcmp(*argv, "-h") == 0) {
        fprintf(stderr, "gun 1.3 (12 Jun 2005)\n");
        fprintf(stderr, "Copyright (c) 2005 Mark Adler\n");
        fprintf(stderr, "usage: gun [-t] [file1.gz [file2.Z ...]]\n");
        return 0;
    }
    if (argc && strcmp(*argv, "-t") == 0) {
        test = 1;
        argc--;
        argv++;
    }
    if (argc)
        do {
            if (test)
                outname = NULL;
            else {
                len = (int)strlen(*argv);
                if (strcmp(*argv + len - 3, ".gz") == 0 ||
                    strcmp(*argv + len - 3, "-gz") == 0)
                    len -= 3;
                else if (strcmp(*argv + len - 2, ".z") == 0 ||
                    strcmp(*argv + len - 2, "-z") == 0 ||
                    strcmp(*argv + len - 2, "_z") == 0 ||
                    strcmp(*argv + len - 2, ".Z") == 0)
                    len -= 2;
                else {
                    fprintf(stderr, "gun error: no gz type on %s--skipping\n",
                            *argv);
                    continue;
                }
                outname = malloc(len + 1);
                if (outname == NULL) {
                    fprintf(stderr, "gun out of memory error--aborting\n");
                    ret = 1;
                    break;
                }
                memcpy(outname, *argv, len);
                outname[len] = 0;
            }
            ret = gunzip(&strm, *argv, outname, test);
            if (outname != NULL) free(outname);
            if (ret) break;
        } while (argv++, --argc);
    else
        ret = gunzip(&strm, NULL, NULL, test);

    /* clean up */
    inflateBackEnd(&strm);
    return ret;
}